FIG. 23 is a conventional operation chart for assembling an upright piano, and FIG. 24 is a sectional side elevation showing the upright piano after assembly. Conventionally, the upright piano is typically assembled according to the following procedure:
(1) First, back posts 1, a bottom beam 2, a top beam 3, etc., are assembled into a back post assembly 5.
(2) After attaching a liner 71 to the back post assembly 5, a sound board 16 having sound ribs 18 and bridges 17 bonded thereto and a pin block 8 are mounted on the back post assembly 5.
(3) After a plate 21 is mounted on the back post assembly 5, and tuning pins 25 are embedded in the pin block 8 via the plate 21, strings W are stretched between the tuning pins 25 and hitch pins 22.
(4) End panels 35 having arms and other component parts attached thereto are fixed to respective opposite sides of the back post assembly 5, and a key bed 26 is mounted between the arms to be supported thereby. In mounting the key bed 26, to effect positioning of the key bed 26 with respect to the plate 21, it is conventionally known to engage dowel pins 76 provided on a front surface of the plate 21 with dowel holes 75 formed in a rear end face of the key bed 26, as shown in FIG. 25(a), thereby positioning the key bed 26 in a longitudinal direction (in the direction of depth of the figure) or alternatively, fix the rear end of the key bed 26 to the plate 21 via a pair of L-shaped mounting hardware pieces 77 attached to the plate 21 at respective left-hand and right-hand potions of the plate 21, as shown in FIG. 25(b), followed by fixing a front portion of the key bed 26, which is free to move in a vertical direction (in the directions of arrows in FIGS. 25(a) and 25(b)), to casing component parts, such as arms.
(5) Keys 27 are placed on the key bed 26 via a key frame 31, and action assemblies 28 equipped with respective hammer assemblies 29 are mounted on the key bed 26. The action assemblies 28 are supported by action brackets 72 each of which has an upper end thereof fixed to the back post assembly 5 by an action bracket bolt 73, and a lower end thereof fixed to the key bed 28 by an action bracket base, not shown.
(6) Regulation (adjustment of operations of each key 27 and the associated action assembly 28 for their correct string-striking actions) and tuning are carried out.
(7) Casing component parts 74, such as a top board 54, a lower panel 55, and an upper panel 56, are mounted, and voicing, finishing, and inspection are carried out to complete the assembly of the upright piano.
However, according to the conventional assembly method, the back post assembly 5 is used as a basis, and a large number of component parts, such as the liner 71, the sound board 16, the pin block 8, the plate 21, the strings W, the end panels 35, the key bed 26, the keys 27, and the action assemblies 28 have to be sequentially mounted. Therefore, all these component parts are usually assembled at the same site. As a result, vast space and large production facilities are required for storage of component parts and assembly work. Such requirement restricts the freedom of selection of assembly sites, and reduces the mobility of production, which makes it difficult to meet the demand of a small or medium scale production or overseas production of pianos.
Further, according to the conventional assembly method, a large number of component parts are sequentially mounted using the back post assembly 5 as a basis, so that tolerances of component part and mounting errors tend to accumulate to bring the component parts out of alignment to a significant degree. Since the key bed 26 is assembled to both the plate 21 and the casing component parts, such as the arms, as described above, the key bed 26 deviates from its proper position with respect to the plate 21 if the plate 21 and the casing component parts are not properly positioned with respect to each other. The casing component parts are typically made of wood, and hence liable to manufacturing errors as well as deformations resulting from distortion and warpage occurring after assembly, so that a certain degree of deviation in position of the key bed 26 from the plate 21 is unavoidable. As a result, the keys 27 placed on the key bed 26, the associated strings W stretched over the plate 21, and the associated action assemblies 28 located therebetween go out of alignment, which requires the action assemblies 28 to be adjusted after assembly e.g. for proper string-striking actions at the cost of much time and labor. This is one of major factors which have been driving up the manufacturing cost of pianos.
Therefore, it is the object of the present invention to provide a method of assembling an upright piano, which makes it possible to assemble an upright piano efficiently and accurately, with smaller space and smaller-scale production facilities.